Mortality patterns reflect fundamental characteristics of societies and help to reveal important changes in population health over time. In order to improve our understanding of such topics, we propose here to examine historical and contemporary mortality patterns for a wide range of countries, including the United States. The work for this project is organized into three parts. The first part consists of an analysis of comparative mortality trends in high-income countries. In the second part, we will continue our efforts to develop publicly accessible data resources for the analysis of global mortality trends, including the developing world. In the third part of this project, we will develop new and better methods for estimating and analyzing mortality in both developed and developing countries. The substantive questions that motivate this project are focused on certain features of recent mortality trends. Specifically, we will examine the pronounced slowdown in the pace of mortality reduction at advanced ages in the United States since around 1980. This trend has affected female mortality in particular, contributing to an overall narrowing of sex differences. We propose to investigate the contribution of key risk factors (especially, smoking and obesity) to these recent trends. To enrich these studies, the project includes a detailed plan for collecting and organizing historical mortality data by cause of death, which will be shared publicly via the Human Mortality Database (www.mortality.org). The project will also address a number of important issues regarding methods for estimating current and historical mortality levels, especially in developing countries. We will develop updated methods of indirect estimation using a new system of model life tables that we have proposed recently. We will also develop new and better methods for quantifying the uncertainty of mortality estimates, especially for countries that lack complete and reliable data from censuses and vital registration. To facilitate this research, we are building a complex database for storing all forms of data that are typically used for estimating both all-cause and cause-specific mortality in national populations.